Study design: Animal study.

Objectives: Umbilical cord-derived mesenchymal stem cells (UC-MSCs) have recently been shown to hold great therapeutic potential for spinal cord injury (SCI). However, majority of the studies have been done using human cells transplanted into the rat with immunosuppression; this may not represent the outcomes that occur in humans. Herein, we present the therapeutic effect of using rat UC-MSCs (rUC-MSC) without immunosuppression in a rat model of SCI.

Setting: Mayo Clinic, Rochester, MN, USA.

Methods: Twelve female rats were randomly divided into two groups, control, and rUC-MSC group, and then subjected to a T9 moderate contusion SCI. Next, 2 × 106 rUC-MSCs or ringer-lactate solution were injected through the tail vein at 7 days post injury. Rats were assessed for 14 weeks by an open-field Basso, Beattie, and Bresnahan (BBB) motor score as well as postmortem quantification of axonal sparing/regeneration, cavity volume, and glial scar.

Results: Animals treated with rUC-MSCs were found to have early and sustained motor improvement (BBB score of 14.6 ± 1.9 compared to 10.1 ± 1.7 in the control group) at 14 weeks post injury (mean difference: 4.55, 95% CI: 2.04 to 7.06; p value < 0.001). Total cavity volume in the injury epicenter was significantly reduced in the rUC-MSC group; control: 33.0% ± 2.1, rUC-MSC: 25.3% ± 3.8 (mean difference: -7.7% (95% CI: -12.3 to -2.98); p value < 0.05). In addition, spinal cords from rats treated with rUC-MSCs were found to have a significantly greater number of myelinated axons, decreased astrogliosis, and reduced glial scar formation compared to control rats.

Conclusions: Our study indicates that intravenous injection of allogenic UC-MSCs without immunosuppression exert beneficial effects in subacute SCI and thus could be a useful therapy to improve the functional capacity among patients with SCI.